D2D communication or Peer to Peer (P2P) communication is a communication service provided via a direct communication link established between terminals without intervention of a network entity such as a Base Station (BS) or an Access Point (AP).
A D2D device acquires device information and service information about at least one device by acquiring synchronization to devices around the D2D device and discovering devices at a predetermined time using predetermined resources. The device information may include identification information, interest information, and application information about the device.
D2D communication may be conducted in conjunction with a cellular mobile communication system, a wireless communication system, or a wideband communication system. A D2D device may search for neighbor devices at a time and resources set by a BS of a mobile communication system, in the same frequency band as allocated to the mobile communication system. The D2D device accesses a network and receives support such as authentication, security, and the like, for D2D communication.
If D2D communication is separated from mobile communication and conducted independently, the D2D device may operate in one of s D2D communication state. However, when the D2D communication states are independent of mobile communication states, interaction between D2D communication and mobile communication is impossible. Accordingly, unnecessary state switching may occur between D2D communication and mobile communication in the related art.